Engineering Division, New York University Abu Dhabi, Abu Dhabi 129188, United Arab Emirates.
Core Technology Platform, New York University Abu Dhabi, Abu Dhabi 129188, United Arab Emirates.
ACS Appl Mater Interfaces. 2022 Dec 14;14(49):54992-55003. doi: 10.1021/acsami.2c19743. Epub 2022 Dec 1.
We report, for the first time, a technique to synthesize free-standing, one-atom thick 2D gold crystals (namely, goldene) and self-assembled 2D periodic arrays of goldene. High-resolution transmission electron microscopy (HRTEM) imaging of goldene revealed herringbone and honeycomb lattices, which are primarily gold surface features due to its reconstruction. Imaging of these surface-only features by a nonsurface characterization technique such as HRTEM is an unequivocal proof of the absence of three-dimensionality in goldene. Atomic force microscopy confirmed 1-2 Å thickness of goldene. High-resolution X-ray photoelectron spectroscopy (HR-XPS), selective area electron diffraction, and energy-dispersive X-ray spectroscopy confirmed the chemical identity of goldene. We discovered the phenomenon of electric field-induced self-assembly of goldene supracrystals with a herringbone structure and developed an electric field printing (e-print) technique for goldene arrays. Goldene showed a semiconductor response with a knee voltage of ∼3.2 V, and / spectroscopy revealed periodic room temperature Coulomb blockade oscillations. These observations are consistent with the theoretical calculations reported in the literature predicting enhanced Coulombic interactions between gold valence electrons and the nucleus in stable 2D gold. Goldene exhibited multiple, intense, and well-resolved optical absorption peaks and several fine bands across the UV-vis region, and we calculated its optical band gap to be 3.59 eV. Magnetic force microscopy measurements of goldene periodic arrays showed a ∼5 mV peak amplitude confirming its ferromagnetism. Optical and magnetic properties of goldene are consistent with those reported in the literature for 2D planar gold clusters with less than 12 atoms.
我们首次报道了一种合成独立的、单原子厚的二维金晶体（即金纳米片）和自组装二维金纳米片周期性阵列的技术。高分辨率透射电子显微镜（HRTEM）对金纳米片的成像显示出人字形和蜂窝状晶格，这主要是由于金的重构导致的金表面特征。通过 HRTEM 等非表面特性技术对这些仅表面特征进行成像，是金纳米片缺乏三维性的确凿证据。原子力显微镜证实金纳米片的厚度为 1-2 Å。高分辨率 X 射线光电子能谱（HR-XPS）、选区电子衍射和能量色散 X 射线能谱证实了金纳米片的化学特性。我们发现了具有人字形结构的金纳米片超晶体的电场诱导自组装现象，并开发了金纳米片阵列的电场印刷（e-print）技术。金纳米片表现出半导体响应，膝电压约为 3.2 V，/ 光谱揭示了室温下周期性的库仑阻塞振荡。这些观察结果与文献中报道的理论计算一致，该理论计算预测在稳定的二维金中，金的价电子和原子核之间的库仑相互作用增强。金纳米片表现出多个强烈且分辨率良好的光学吸收峰和几个在 UV-vis 区域的精细带，我们计算出其光学带隙为 3.59 eV。金纳米片周期性阵列的磁力显微镜测量显示出约 5 mV 的峰值幅度，证实了其铁磁性。金纳米片的光学和磁学性质与文献中报道的二维平面金簇（少于 12 个原子）的性质一致。
